"Decades from now, when historians evaluate the war, what will they say about us? Will they claim that our victory was ultimately fruitless? That it failed to secure a lasting peace, or worse, that it was only a prelude to far greater horrors that now lay ahead?"

Although the death of the Prophet of Truth at the Ark during the endgame of the Covenant War saw the ultimate defeat of the Covenant and humanity's truce with most Sangheili, represented by the Swords of Sanghelios, it was not long after the end of the war that rogue splinter groups began to rise from the remnants of the hegemony. With large amounts of former Covenant matériel at their disposal, many of these disparate remnants opposed both the UNSC and the former members of the Covenant who favored a policy of peaceful cooperation, an approach most visibly embodied by ArbiterThel 'Vadam. The UNSC's aggressive rearmament (largely made possible by the acquisition of Forerunner technologies and exemplified by the colossal warship UNSC Infinity as well as the rapid creation of hundreds of new Spartan supersoldiers) combined with the Office of Naval Intelligence's shortsighted approach to neutralize their former enemies, did little to ease the concerns of more hostile elements within Sangheili society.

While Sanghelios remained locked in a state of civil war between various factions, in part due to the clandestine activities of the Office of Naval Intelligence, a former Sangheili Shipmaster known as Jul 'Mdama created his own revival of the Covenant. During his time in ONI captivity on ONIRF Trevelyan, 'Mdama had learned that the Didact, a mighty Forerunner general with a hatred for humans, was trapped inside a Forerunner world known as Requiem. After escaping Trevelyan, 'Mdama began to gather followers in order to travel to Requiem and unlock the world's secrets, intending to use the Didact as a motivating force for his followers, but also a new spiritual voice for his people and a chance to exact vengeance on humanity.[8]

Humanity found itself facing renewed internecine struggle as well. While the Insurrection had ceased as a major conflict at the start of the Covenant War in 2525, some surviving colonies still harbored former Insurrectionists as well as individuals sympathetic to the cause of colonial secession.[9] Some colonies, including Venezia, cut off all ties with the UEG under the pretense that Earth had abandoned them during the war.[10] Some rebel groups managed to obtain large amounts of Covenant and UNSC weapons and equipment circulating on the black market.[11]

In January 2553, elements of the New Colonial Alliance led by UNSC defector Ilsa Zane (the only survivor of the SPARTAN-IV program's prototypical stage) infiltrated the UNSC Infinity disguised as construction personnel and captured most of the bridge crew, using them as hostages. They then secured the ship's bridge in the hope of capturing the prototype UNSC flagship, threatening to vent the ship's atmosphere and kill everyone aboard it.[12] The attempt was foiled by the first team of SPARTAN-IVs (who had recently been brought aboard) and the insurgents were all killed or captured. The prisoners revealed Admiral Mattius Drake as the organization's leader.[9]

With Truth dead, High Charity destroyed, and the Ark heavily damaged after Installation 08's firing, some of the remaining Jiralhanae forces tried to rebuild their tattered strength to continue their war of conquest.[16] Even though the Jiralhanae eventually collapsed into various civil wars, they still posed enough of a threat that Sangheili commanders kept up the offensive against them for at least another six years, even as they continued to lose irreplaceable warships and the war continued with no end in sight. This forced the Swords of Sanghelios and their UNSC allies to fight in a two-front war, one was the Blooding Years against other Sangheili who remained loyal to the Covenant religion and the other was the continued conflict against the Brutes, who were also engaged in numerous civil wars.[17]

Some fanatical Sangheili, who did not associate themselves with any particular Sangheili-led faction, continued to hunt down and eliminate all Jiralhanae they discovered, as well as any forces under their control. A notable example of such Sangheili was the Silent Shadow squad under the command of First Blade Resa 'Azavayl.[18] They wiped out Jiralhanae forces across multiple systems, slaughtering them at an armory on the fourth moon of Victors' Truth, aboard the stolen Covenant corvetteAdherent, at the northern highlands of Thalia, aboard a derelict colonial substation orbiting Sansar, and eradicating the last remaining members of ChieftainTartarus' crew aboard the Covenant cruiser Rapid Conversion. Ultimately they found themselves face to face with Atriox, leader of the Banished. When Atriox extended the Silent Shadow an offer to join the Banished, Resa refused, declaring that he and the Banished deserved death for their "sins". Atriox had mentioned to them that he was not involved in the betrayal and massacre of the Sangheili,[19] and the squad began to view him as "other".[20] Resa's brothers in arms, believing Resa was blinded by old loyalties and festering delusions of vengeance, turned on their leader and killed him. Afterwards, Atriox allowed the remaining members of the Silent Shadow to join the Banished, offering to reward them with "blood and sport and spoils".[18]

The Covenant had strategically settled Jiralhanae populations on resource-rich worlds as a planetary garrison force to protect the worlds from potential raids. While the Jiralhanae continued to inhabit these worlds after the dissolution of the Covenant, they were unable to mine or utilize the resources because of their own lack of sufficient technology. With the Covenant's supply chains gone, the Jiralhanae quickly found their supplies near depletion. This was one of the primary reasons for their raids on Sangheili colonies after the Human-Covenant war; despite quite literally living on top of plentiful resources, the Jiralhanae were entirely dependent on the already processed supplies of other races due to their technological backwardness. However, the Jiralhanae could not sustain themselves via raiding alone in the long term and their supplies began to wear thin, leading to an impending species-wide famine in 2558 and an increase in Jiralhanae attacks across Sangheili and Kig-Yar colonies as a result. During this crisis, the Jiralhanae ChieftainLydus and his clan were willing to initiate peace talks with ArbiterThel Vadam and the Swords of Sanghelios, overseen by the UNSC.[21] However, the negotiations were interrupted by Covenant mercenaries hired by the New Colonial Alliance.[2]

The Jiralhanae were supplied with powerful new weapons by their San'Shyuum leaders. When the San 'Shyuum went into hiding, the Jiralhanae began to lose order and started to fight amongst each other. This ultimately gave the upper-hand to their Sangheili opponents. As of 2559, the Sangheili are currently winning their war against the Jiralhanae.[15]

After the Human-Covenant war, many Sangheili still worshiped the Forerunners as gods. A religious sect known as the Servants of the Abiding Truth, led by war veteran Field MasterAvu Med 'Telcam, took to believing that any tampering with Forerunner relics was heresy, just as most Sangheili did before the founding of the Covenant. As a result, 'Telcam and his followers grew angry with ArbiterThel 'Vadam's government. After winning the favor of several keeps and mustering a small space fleet, the Servants led an uprising in the state of Vadam. They initially held the upper hand, but the tide turned when UNSC Infinity arrived and intervened on behalf of the Arbiter, shooting down a rebel destroyer and firing a MAC round into massing rebel ground forces besieging 'Vadam's keep. The ONI black operations team known as Kilo-Five, however, hoped to keep the planet destabilized for fear that the Sangheili would oppose humanity if they were politically unified, and so they used their prowlerPort Stanley to destroy some of 'Vadam's cruisers. This caused a temporary stalemate, but the battle continued until 'Vadam and his allies emerged victorious. The Servants retreated off-world to New Llanelli to recover from their losses, putting the war on hold.

During a Ferret team training exercise on Neos Atlantis on October 14, 2553, Dark Moon Enterprises attempted to publicly expose the secrets of the Spartan-IIIGamma Company illegal augmentations, believed to be because such a revelation would cripple ONI and create a power vacuum that Dark Moon could then fill. To this end, former ONI CommanderOta Gallo helped reporter Spencer Hume drug Olivia-G291 with nicothiotal so that Hume could question her and use the information to expose the illegal augmentations. However, team leader Veta Lopis quickly realized what was happening and had the rest of the Ferrets intervene, leading to an assassination attempt on Mark-G313 in a service hallway by Gallo. The attempt failed, but Hume was accidentally killed by Mark in the process. Mark disposed of Hume's body out of an airlock with the help of Ash-G099, but they were noticed by Commander Svenson of Oscar Squad who the training exercise was against. At the same time, Gallo erased all of the security footage of the incident in order to be able to avoid detection.

As the Ferrets regrouped in the suite acting as their safe house, they were visited by Rear AdmiralSerin Osman and Commander Svenson who accused Mark of murder, though he couldn't prove it. Veta denied the accusations and suspected Oscar Squad had gone too far in the training exercise. Osman gave them two hours to discover the truth and the Ferrets managed to identify Gallo and her connection to Dark Moon. It was quickly realized that it was not a training exercise gone wrong but an attempt to expose them and cripple ONI. In order to draw Gallo into a trap, Olivia sent a message detailing what they had learned from Hume's COM pad to both Osman and Gallo. Gallo, needing to retrieve the COM pad which proved she was Hume's source, attacked the suite with two other Dark Moon operatives. The Ferrets were able to eliminate Gallo and her men, but Olivia was severely injured in the process and Hume's COM pad damaged. When Osman returned, the Ferrets turned over the COM pad to her and Veta pinned Hume's death on Gallo covering her tracks. Though Osman was obviously skeptical, Mark backed up Veta's story without hesitation and Osman accepted it.[32]

The Ferrets were able to locate the Keepers' Salvation Base on Taram which had been built in the middle of the Forerunners Suluhu Contemplarium on the orders of Intrepid Eye as part of another one of her plans. As they searched the base, the Ferrets located a Dark Moon Turaco which had been used to move the bodies of the Tuwa's to Salvation Base after their organs had been harvested and placed in cryo-jars. Inside the detention center, Veta and Mark-G313 found the bodies of the family staged to look as if the Keepers were the killers, but realized quickly that the whole scene was staged. As Blue Team arrived, the Ferrets attempted to stop the Dark Moon operatives from escaping, only to have them captured by Castor. After Linda-058 armed six HAVOK tactical nuclear weapons, both teams escaped in the Turaco as the nuclear detonation destroyed Salvation Base and ninety percent of the Keepers forces stationed there.

On the Silent Joe, Veta insisted upon continuing the investigation with the connection between the Tuwa's and the asteroidea quickly being realized. Using forensic evidence taken from the Tuwa's recovered bodies, the UNSC was able to track the murder scene to the lab on Gao where the vaccine experiments had been performed. However, by the time that they arrived, Castor had already raided and destroyed the lab, having learned of its location from the captured operatives. With the help of the facility's captured director, Castor had continued his pursuit of Dark Moon for revenge for Dark Moon framing him. Veta confronted Gao President Arlo Casille who admitted to allowing Dark Moon to use the laboratory in exchange for their getting the UNSC to get the Keepers off of his back. While he knew about the Tuwa family, he hadn't reported it out of fear of an invasion if the UNSC knew. Realizing that Dark Moon had set up both the Keepers and Gao to take the fall, Casille pointed the Ferrets towards Pinnacle Station at Meridian whose smart AIAdministrator Sloan had recommended Dark Moon to him in the first place.

At the same time, Intrepid Eye learned of the destruction of Salvation Base and the failure of the attempt to frame the Keepers. To keep from being found out, Intrepid Eye dispatched her remote aspect Oriel, LieutenantBartalan Craddog who she was blackmailing and the ONI security unit Papa-10 to retrieve the cryo-jars holding the Tuwa's organs and to execute the Dark Moon couriers. At Pinnacle Station, Papa-10 successfully eliminated the Dark Moon couriers and retrieved the cryo-jars, but were ambushed by the Keepers led by a vengeful Castor. Craddog managed to kill Orsun and several Kig-Yar with an M41 SPNKR, but the Keeper attack proved to be too overwhelming for Papa-10 whose three survivors were forced to flee to the surface of Meridian, chased by Castor and three Jiralhanae.

Shortly after the firefight, the Ferrets and Blue Team arrived to find the aftermath. Thinking that they were associated with Papa-10, Sloan explained that he had rented Dark Moon a hidden berth at their request and directed the teams to the location on Meridian where Papa-10 and Castor's forces had landed. Though suspicious of the circumstances, the Ferrets and Blue Team followed Papa-10's survivors into an abandoned mine where they helped to eliminate Castor's forces. However, Papa-10 attacked, seriously injuring Fred-104 and fleeing towards an extraction point suggested by Sloan. Both Castor and Veta managed to hang onto Papa-10's vehicle and Castor succeeded in eliminating two of the operatives, but was knocked off of the vehicle after Veta tried and failed to make an alliance with him against their common enemy. After placing C-12 explosive around the cryo-jars, Veta abandoned the vehicle and watched as it met up with a Pinnacle Station utility skiff piloted by Craddog. With the remaining Papa-10 operative pointing an assault rifle at her and unwilling to let them get away with the cryo-jars containing the Tuwa's organs, Veta detonated the explosives. The blast killed the last Papa-10 operative and Craddog and destroyed the cryo-jars, the utility skiff and Intrepid Eye's remote aspect Oriel, foiling the plot.

In the aftermath, Rear AdmiralSerin Osman had the Ferrets returned to the Mill to complete their training and warned Veta that a greater threat was coming that she needed the Ferrets ready for. Additionally, ONI concluded that Craddog had been working on his own initiative to initiate Project SLEEPING STAR in the absence of any orders telling him to do so. Intrepid Eye avoided discovery as the true culprit, though she was unable to confirm the death of Castor and the destruction of his cell with the destruction of Oriel, one of her oldest and most useful remote aspects. Though Rear AdmiralSerin Osman ordered Project SLEEPING STAR shut down, Intrepid Eye manipulated the orders so that it continued in secret aboard the Argent Moon as the bioweapon project was too important to her plans to be allowed to be stopped.[33]

Blue Team reunited with their previous leader, John-117, on July 25, 2557, after which they embarked on a new series of missions for over a year.[34] During one such mission, in early 2558, Blue Team managed to stop fanatical ex-Covenant, who had hijacked an M510 Mammoth and tried to use it to ram a new ONI research facility's main fusion reactor. The Spartans prevented the disaster without any civilian casualties.[35]

On March 29, 2554, Rudolf Schein, one of the recently inducted Spartan-IVs, who was secretly associated with the United Rebel Front, murdered another Spartan trainee, Hideo Wakahisa, during his attempt to recruit him on Spartan-IV training station. Realizing the discovery of his true loyalties was imminent, Schein had covertly installed several explosives throughout the station and slung a bandolier of grenades across his chest. However, Spartan Operations Chief of StaffJun-A266 managed to neutralize Schein by kicking him out into space, where he died before he could be recovered.[40]

In 2554, a former Covenant fleet led by Merg Vol invaded the UNSC research colony Draetheus V and its moon, X50, in search of Forerunner relics, beginning a major battle which marked one of the first missions of the UNSC's recently formed Spartan Operations branch.[41] The battle saw significant losses on both sides and the planet itself was nearly destroyed by Vol's use of X50, which was in fact a Forerunner superweapon with the capability to destroy planets. The main hostilities concluded with Spartan Sarah Palmer killing Vol and sabotaging X50's main weapon, bringing the Covenant's quest to a halt. However, the Covenant returned when a looping Forerunner code began emanating from X50.[42] After arriving at the source of the signal, Spartan Palmer discovered that the source was the remains of Spartan Edward Davis, who had died during the battle. The installation disintegrated Davis's corpse and encapsulated it in an unknown device, and with the help of a Pelican, Palmer took the remains of her comrade with her.[43]

In 2555, renowned human scientist Doctor Luther Mann discovered the location of Installation 07. The Office of Naval Intelligence subsequently sent a research detachment to study Zeta Halo. While inspecting the ring's custodial systems, Mann discovered a Forerunner timer that was counting down to the Halo Array's activation in five weeks. Both the UNSC and Swords of Sanghelios decided to travel to what remained of Installation 00 to manually stop the timer. Members of the group came from both factions involved and met aboard the warship Mayhem. When the HuragokDrifts Randomly activated the Portal at Voi for the first time since the Battle for Earth in 2552, a Retriever Sentinel, sent by 000 Tragic Solitude, emerged through the portal and began strip-mining the area around the structure, forcing the UNSC Endeavor and accompanying small craft to engage it. Mayhem proceeded to enter the portal to travel to the Ark. Upon exiting slipspace, the corvette was immediately engaged by more Retrievers, and was heavily damaged in the process, crash-landing on the surface of the installation. The group set out to go to the Citadel by foot, encountering some of the installation's ambient life, including predatory species 'native' to the installation. Eventually arriving at the Citadel, the group shut down the firing of the rings.

Before the group could stop the firing of the rings, however, Tragic Solitude dispatched a fleet of Retrievers through the portal to strip-mine Earth and the rest of the Sol system. The UNSC Home Fleet engaged the invading force, initially repelling them but soon being overwhelmed by the Forerunner constructs' sheer numbers. Eventually there were only a dozen human ships left, which charged into the Retrievers in a last-ditch defense of Earth. However, due to the actions of the party at Installation 00, Tragic Solitude recalled the Retrievers, and they retreated through the portal back to the Ark.[44] However, Tragic Solitude resumed his attack on the group and was destroyed by Bobby Kodiak at the cost of his own life. With the threat neutralized, the UNSC sent a fleet to the Ark to investigate and the Mayhem was rescued by the UNSC Witness. Plans were made to repair the Ark using the Retriever Sentinels by directing them to mine lifeless systems and it was also decided to begin setting up research outposts on the installation.[45]

Several of the more fanatical splinter factions of the Covenant continued the practice of glassinghuman colonies after the end of the Covenant War. The colony of Cleyell fell victim to such an attack in 2556.[47] The UNSC Cascadia moved into orbit of Cleyell weeks later to deploy Army and Marine search-and-rescue teams to relieve the stranded colonists on the surface.

After being recovered by the UNSC Rubicon, 343 Guilty Spark, the former Monitor of Installation 04, became determined to locate the Forerunner known as the Librarian whom he claimed was still alive. Spark hijacked the Rubicon and put the crew into cryo to search for the Librarian.[48] However, the ship crashed on Geranos-a in 2554, leaving the crew dead. Spark survived the crash by transferring himself into an armiger made out of parts salvaged by the Rubicon from Installation 00 and activated a distress signal which was eventually picked up by a cargo ship in 2557 and relayed to ONI.[49]

During an operation to get a Luminary, the crew of the Ace of Spades was captured by the ONIProwlerUNSC Taurokado. ONI agents seized Little Bit, his projections of the Spirit of Fire's possible flight path, recordings and even the crew's personal belongings. As Little Bit refused to cooperate with the agents, Agent Hahn forced Rion Forge to order the AI to comply, while also seizing all of the crew's assets and salvage, including a warehouse of items they had amassed. However, while aboard, Rion managed to hack the Prowler's communications and learned of the distress signal from the UNSC Rubicon on Geranos-a which clearly held a great deal of interest for ONI. In an effort to force ONI to return their stolen property, the Ace of Spades crew chose to investigate and salvage from the Rubicon in hopes of finding what ONI wanted.[49]

Using the data taken from the Ace of Spades and Little Bit, the Taurokado was able to locate the debris field of the Etran Harborage in the Korinth Prior system and undertook a mission to investigate.[49]Taurokado conducted scans which showed that this debris field was composed of 94% naturally-occurring materials and 4% Forerunner materials, with 2% untraceable, and that of detritus size, 9% neared the scale of small lunar satellites while 84% were the size of the ship or smaller. Taurokado's sensors also revealed that low-level shielding sporadically surrounded structures of Forerunner origins.[51]

At 0924 hours (MST), Taurokado commenced site surveys of identified Forerunner structures. Fireteam Apollo was deployed to investigate a number of these structures. At one, designated "Site 012", Apollo uncovered configurations matching the Sarcophagus at Onyx. At "Site 042" they confirmed that the debris had formerly been a shield world. Apollo also found evidence of Forerunner Sojourner-class dreadnoughts and a Flood infestation at "Site 029" and "Site 021", respectively. At "Site 037", Apollo recovered identifiable human materials. Analysis confirmed that these had belonged to the Spirit of Fire, including war materiel and Titanium-A battleplating. However, no evidence of survivors was detected by either Apollo or Taurokado.[51]

At 1642 hours (MST), Taurokado made contact with a hostile Covenant remnantbattle group led by Gek 'Lhar.[49] Fireteam Apollo was distaptched in F-41 Broadsword fighters to intercept the enemy. After dispatching two waves of Type-31 Seraph fighters, Apollo fell back to the Taurokado. At 1714 hours (MST), the Taurokado released sensor buoy "B89-7" and slipped from the system, in accordance with protocol.[51]

With the Taurokado busy investigating the debris field, the Ace of Spades made its way to Geranos-a where they discovered and investigated the wreckage of the Rubicon, salvaging many things from it, including the armiger of 343 Guilty Spark. Spark was able to access the database of the Ace of Spades and became determined to continue his mission to find the Librarian using the Ace of Spades. With the Taurokado and UNSC Bad Moon Rising approaching, Spark helped the Ace of Spades escape into slipspace with the intention of taking the ship to the Etran Harborage to get an upgrade seed. To get the crew to cooperate with him, Spark promised to allow them to salvage the Forerunner technology present on the shield world, unaware that it had been destroyed by the UNSC Spirit of Fire in 2531.

When the Ace of Spades returned to the debris field, it was to find Gek 'Lhar and his forces working to salvage Forerunner technology from the wreckage. As the Ace of Spades dodged the Covenant, the UNSC unexpectedly returned to the system with a massive fleet. The UNSC fleet unleashed a massive nuclear bombardment upon the debris field in an act of asset denial, blowing the Etran Harborage debris field to bits and disrupting its gravity with the system's dwarf star. Anything that wasn't destroyed by the bombardment would likely be pulled into the star's gravity, eradicating the remnants of the Etran Harborage completely. Rather than fight, Gek 'Lhar fled to slipspace the moment the UNSC fleet opened fire while Spark managed to get the Ace of Spades out in time.

In order to continue his mission, Spark set course for the former Forerunner world of Triniel where a Builder facility was located to get the upgrade seed that the Ace of Spades needed. Spark provided the crew with a history of the Forerunners and the galaxy and offered to help them retrieve their belongings and data and search for the Spirit of Fire if they would help him complete his search for the Librarian, a deal that they ultimately accepted. Arriving to Triniel in July 2557, the Ace of Spades salvaged a lot of Forerunner technology from the Builder facility while Spark repaired problems with his armiger and created an upgrade seed for the ship. Though Spark intended to use the planet's communications satellites to contact the Domain, he ultimately deactivated them before they could reboot as the crew wanted to leave Triniel free from mass exploitation as Triniel was a planet-wide mass grave for the population who had committed suicide to avoid the Flood. Spark later attempted to access the Domain, but was blocked by Catalog.

With a bounty put upon them by Gek 'Lhar and ONI offering a deal to trade for their stolen data, credits and belongings the crew agreed to a meeting at Port Joy on Binterall in August. ONI kept their end of the bargain and turned over a clean copy of all of Little Bit's projections and video recordings as well as the crew's belongings, while the crew claimed that they had only recovered a data core upon which was a fragment of Spark. After the meeting was attacked by bounty hunters, the crew fled and used the upgraded Ace of Spadesslipspace drive to get past an attempt by the Taurakado and Bad Moon Rising to stop them. However, in the process Spark's armiger was revealed as was the fact that the Ace of Spades had received upgrades to its engines as well as illegal cloaking technology due to how well it had hidden until Spark brought the ship in to rescue the crew.[49]

On September 1, 2557, the Ace of Spades arrived at Earth with the cloaking technology from the upgrade seed making the ship completely undetected on approach. The ship landed at Mount Kilimanjaro while Spark used his fragment to infect and shut down the ONI facility at the Voi while also using his fragment to search for data on Catalog who had been hounding ONI since 2552. Before turning herself in for review, the AI Thea happened to detect the Ace of Spades and sent a quick warning seconds before the facility completely shut down. The AR team and Fireteam Apollo managed to blow their way out of Hanger One and headed for Kilimanjaro to stop the crew and Spark.

Spark led the Ace of Spades crew into Mawenzi where Rion's touch as a Reclaimer allowed them access into a Forerunner installation inside of the mountain where Rion deactivated a hard light barrier protecting a Lifeworker pod on a platform and activated a hard light bridge to the platform. Before Rion could deactivate the barrier around the pod, Spark finally admitted the truth to her: that her father had died sacrificing himself to destroy the Etran Harborage. Enraged at Spark keeping the truth from her, Rion attacked the armiger before she decided to deactivate the barrier and end their deal and alliance. However, before the crew could leave, Agent Hahn, Fireteam Apollo and the AR team arrived in the facility and blocked their exit. Spark deactivated the light bridge on Rion's request before he entered the column of light surrounding the Lifeworker pod, but the Ace of Spades crew were left outnumbered and with no means of escape as the ONI forces worked to bring the light bridge back online.

Spark's entry into the column awakened a personality imprint of the Librarian stored within the pod. The Librarian greeted Spark by his original human name of Chakas and expressed regret for the pain she had caused him and marvel over the being he had evolved into. The Librarian revealed to Spark the awakening of both her imprint and the Didact at Requiem, but wouldn't go further into details about it. Spark expressed his desire to bring his friends Riser and Vinnevra back, but the Librarian reminded him of what Spark had gone through as Chakas, bearing the essence of Forthencho, Lord of Admirals. The Librarian revealed to Spark that his friends were at peace, their gene song quiet and cautioned him against going to the Domain to be with them as he would only find echoes of them. The Librarian refused to join Spark using an armiger and instead helped him understand that he had found the friends he had been searching for for so long amongst the Ace of Spades crew.

The Librarian announced that she would join her other imprints at the Absolute Record while humanity had to be given the tools to uphold the Mantle of Responsibility and the knowledge to maintain the Domain. The Librarian offered Spark a choice: to join her at the Absolute Record or to remain behind with his friends. The Librarian offered Spark a small etched box in case he chose to remain and ordered him to "find what's missing. Fix the path. Right what my kind has turned wrong." Spark chose to remain with his friends and the two promised to meet again.

As Spark and the Librarian met, the ONI forces managed to reactivate the hard light bridge while no sign of a way out was discovered. While the crew tried to figure out their options, the Librarian departed to the Absolute Record blinding everyone in the cavern. Before her departure, all of the humans in the cavern beheld the Librarian briefly and she communicated a message to Rion at least which ordered her to take care of Spark, calling Spark more fragile and important than she could ever know. Spark shifted his armiger into a combat configuration and formed a hard light rifle to face off with ONI forces who opened fire as the Ace of Spades crew took cover. Spark then used his light rifle to bring down rocks onto the light bridge which forced the ONI team and Spartans to retreat after which Spark shut it down and smashed the terminal in an effort to prevent it from being reactivated.

Using the translocation pad in the platform, Spark teleported the Ace of Spades crew to just below the summit of Mawenzi and remote-piloted the Ace of Spades to pick them up. Though military drones swept the area before the ship arrived, Spark was able to cloak the crew until they were gone. After getting what he wanted from the ONI facility, Spark pulled his fragment out as well. Several hundred people witnessed the light from the Lifeworker pod departing the Earth's atmosphere while ONI was left to examine the Forerunner installation which they realized had most likely contained a personality imprint of the Librarian.[49]

Following the escape from Mount Kilimanjaro, Spark revealed to Rion that he knew of John Forge's fate because, during his time with the UNSC and ONI during the conclusion of the Human-Covenant War, he had gained access to many sources of data. From one, Spark had discovered one or more recovered preprogramed maintenance sheds and data drops left behind by the UNSC Spirit of Fire in hopes of leaving a trail. The data included a message to Rion from her father and left as part of a promise by Serina and Captain James Cutter. Spark provided Rion with the message, her father's final goodbye to his daughter.

A week after the mission, the crew held a ritual goodbye at Spark's request to honor those that they had lost. During it, Spark let go of his past and all that he had lost and accepted his new future with the crew, singing for all that he and his friends had lost along the way and writing their names on a nearby stone ledge. Spark admitted to Rion that his intention all along had been to access the Domain with the Librarian's help to find the ghosts of his friends and either bring them back as geas or join them. Spark revealed that the Librarian had given him a coordinate key for a safe place, but refused to elaborate further. Promising that there would be no more lies, Spark offered his services as the shipboard AI of the Ace of Spades.

On September 7, the Ace of Spades departed Earth undetected by the Home Fleet. The crew was left to ponder what their next move would be as both Gek 'Lhar and ONI would be after them. Rion announced that they needed to get the bounty off of their heads while showing that they weren't the enemy of the UNSC and ONI. She decided that they would finish what they started and find the Spirit of Fire and all the people aboard who her father's sacrifice had saved with Spark expressing confidence that they would succeed. Rion suggested that afterwards, with the salvage from Triniel leaving them in a position where they would never lack for credits or resources again and the Ace of Spades upgrades, they had the luxury of choosing what they would do next.[49]

By 2554, Jul 'Mdama had already gathered formidable numbers of followers and a powerful fleet which discovered Requiem, but were unable to enter the thoroughly sealed shield world. In orbit above the planet, however, was the wreckage of the UNSC Forward Unto Dawn, carrying the legendary Master Chief, SPARTAN John-117, and his deterioratingAI companion Cortana, drifting in space since the end of the Covenant War in 2552. Upon discovering the derelict vessel in July 2557, 'Mdama's Covenant forces attacked the Dawn in hopes of deterring any potential efforts by the humans to access the shield world. During the ensuing skirmish, Requiem's automated systems pulled both the Dawn and the Covenant force surrounding it through the world's outer shell and down to the planet's surface.[53]

On Requiem, both John-117 and the Covenant forces that hunted him were attacked by the mechanical Promethean forces that occupied the structure. In the core of the installation, the Master Chief accidentally released the Ur-Didact from his 100 millennia-long imprisonment. Bent on preventing mankind from attaining the Mantle, the Didact departed the core and allied with 'Mdama's Covenant.[52] Meanwhile, UNSC Infinity, lured to Requiem by Forward Unto Dawn's distress signal, crash-landed inside the shield world. Making way for the crash site, the Master Chief reunited with the UNSC and aided in the defense of the stranded flagship from the Covenant and the Didact. However, due to a difference of opinion between Infinity's captain Del Rio and John-117, the latter was left facing the Didact alongside Cortana while Infinity returned to Earth.[54]

The Didact left Requiem on his flagship Mantle's Approach, intent on acquiring the Composer, a Forerunner device with the power to enslave all of humanity. With John-117 and Cortana in pursuit, the Didact attacked Ivanoff Station, a UNSC research facility near Installation 03 and the location of the Composer. Despite the UNSC's best efforts, the Didact was able to acquire the Composer and used the device on the occupants of the station, but John-117 was saved by genetic enhancements provided by the Librarian's personality construct back on Requiem.[55]

The Didact then headed for Earth with the Master Chief acing across the hull of Mantle's Approach aboard an F-41 Broadsword fighter. With support from Infinity and the UNSC Home Fleet, John-117 made his way inside Mantle's Approach and confronted the Didact, but not before the Forerunner used the Composer to digitize the population of New Phoenix, URNA. With the aid of a rampant Cortana, the Master Chief was able to send the Didact plummeting into a slipspace rupture, and destroy his ship with a HAVOK nuclear warhead. Using the last of her power, Cortana was able to translocate John away from the blast, saving his life at the cost of her own.[56] Left adrift in space, he was later recovered and brought aboard Infinity and debriefed by the UNSC Security Council shortly afterward.[57]

After falling into the slipspace rupture, the Didact was teleported to the surface of Installation 03, where he quickly recovered and killed Spartan Black Team and a UNSC science team. Meeting with the monitor859 Static Carillon, the Promethean commander then entered the Composer's Forge via a portal, intending to continue his crusade against humankind.[57][58]

In late July of 2557, Jul 'Mdama's reformed Covenant faction invaded Gamma Halo in an attempt to use the Forerunner Conduit to open slipspace portals throughout the installation in order to transport a massive Promethean force onto the ringworld, which would aid in the Covenant's takeover of Installation 03. Other portals were also opened throughout the galaxy, including one in New Phoenix. Eventually, the attack was repelled due to the efforts of two Headhunters and the UNSC Marine Corps stationed on the installation.[59] Meanwhile, researchers at the New Phoenix ONI facility were studying a Forerunner artifact. When the portal opened in the city, Jul's Covenant launched an assault on New Phoenix. One of the Headhunters was tasked with rescuing ONI research team. Upon rescue, they decided that they needed to use the Conduit to close the portals in the city and end the invasion.[60] The Spartan aided researchers in their effort, fighting past Covenant and Promethean forces, and delivered the Conduit to the Forerunner artifact. The artifact released a charge which shut down all portals in the city. After this, he was extracted by another Spartan.[61]

Due to the loss of contact with the science team on Gamma Halo, Fleet Admiral Terrence Hood sent Blue Team, consisting of Fred-104, John-117, Kelly-087, and Linda-058, to investigate.[57] Upon their arrival at Installation 03, Blue Team found the corpses of the scientists as well as Team Black. They soon discovered the Composer's Abyss and a portal leading to the Composer's Forge, an installation housing six new Composers.[57] There they encountered the Didact and his new batch of Promethean constructs. During the ensuing firefight, Static Carillon transported Installation 03 above the Composer's Forge per the Didact's request. The Didact acquired one of the Composers in the Forge and departed for Gamma Halo with the plan to use the ring to wipe out humanity. However, the monitor decided to help the Spartans defeat the Didact due to his abhorrence of the Promethean machines.[58]

After surviving another clash with the Didact on Installation 03, John-117 confronted the Didact in the control room while the rest of his team returned to their Longsword fighter. The Master Chief used the Activation Index to disable the Halo's safety protocols, allowing Static Carillon to eject the entire plate section housing the control room. The segment fell on the Composer's Forge, presumably destroying the Composers housed there. The resulting explosion reduced the Didact to ashes.[62]

Static Carillon teleported John-117 out of the control center just in time and bade farewell to the Spartans before taking Gamma Halo to an undisclosed location. Blue Team returned to Earth, where the Master Chief was debriefed by Fleet Admiral Hood. While Lord Hood believed the Didact was dead, the Master Chief cautioned that it was best to consider him "contained". Afterward, John and Blue Team departed to carry out missions on their own in spite of Lord Hood's suggestion that the Master Chief should stand down.[62]

While the Didact was seemingly quelled, proving a setback for the Promethean-Covenant alliance, it did not result in their defeat. Six months later, in February 2558, Infinity returned to Requiem with a fresh complement of Spartans, determined to conquer the planet at any cost with the intent of studying the Forerunner relics therein. In the interim, Requiem had been occupied by Jul 'Mdama, who now held sway over the local Promethean armies. The Covenant ships in orbit around the planet were swiftly defeated and scattered, demonstrating the technological advancement of the UNSC since the end of the last war.

Significant numbers of UNSC military forces were deployed on Requiem, including detachments of Spartan, Marine, Navy, Air Force and Army forces on Requiem. Arriving on the planet's surface, Majestic, Crimson and other SPARTAN-IV squads began to disrupt Covenant operations across Requiem and recover Forerunner artifacts for study. The Covenant in turn made numerous attempts to destroy Infinity while also trying to gain access to the stored memories of the Forerunner known as the Librarian.

The campaign ultimately ended in Requiem's destruction when Jul 'Mdama set the planetoid on a collision course with the sun. Both sides evacuated the doomed system, each possessing their own half of the Janus Key. After ONI's failed attempt on her life Dr. Catherine Halsey was convinced that the UNSC was working against her and agreed to work with Jul 'Mdama to accomplish her personal goal of reuniting the halves of the Janus Key to unlock the Absolute Record.[63]

The events revealed a significant security breach in the UNSC, with Spartan Vladimir Scruggs exposed as a traitor along with the implicit presence of a higher-ranking leak within the organization. The Covenant's attack itself was a major setback to Thel 'Vadam's efforts to make peace with the Jiralhanae.[67] Captain Lasky later discovered that the attack on Ealen IV had not been orchestrated by the Covenant remnants, but by Daniel Clayton, a UNSC captain and defector to the New Colonial Alliance bent on revenge against Lord Hood, who hired Vata 'Gajat and his troops to stage the attack.[2]

After their failed assault on Ealen IV, 'Gajat and Captain Clayton lured Admiral Hood and the UNSC Infinity into a trap using a freighter, the Pilgrims' Pride which sent out a distress signal that was later picked up by Infinity. An ambush was sprung when the freighter set itself to self-destruct after being towed into one of Infinity's main bays and launched multiple automated craft that engaged the UNSC forces. The attack was repelled by the SPARTAN-IVs of Infinity.[68]

After the ambush, the Infinity crew discovered that the assault crafts aboard the Pilgrims' Pride were from the long-lost UNSC Spirit of Fire.[68] With the Spirit's possible location found, Lord Hood authorized Palmer to conduct a search-and-rescue in Oth Lodon's system. However, Captain Clayton launched a surprise attack against the UNSC flagship using a Covenant battle station's energy projector.[2] The strike disabled Infinity, but Commander Palmer and Fireteam Majestic were able to seize the NCA station. They also destroyed 'Gajat's ship, which was preparing to attack Infinity, killing the mercenary leader.[69]

Many members of the Infinity crew were killed in the attack, including Commander Bradley, while Fleet Admiral Hood was left paralyzed. Captain Clayton was detained in Midnight Facility while Infinity remained under repair for a month.[69][70]

After years of diplomatic work, peace talks were finally scheduled between humanity's Unified Earth Government and the Sangheili. The convocation was held in a regional embassy in a densely populated city on Biko in the human Outer Colonies. Richard Sekibo, the revered ambassador of the Outer Colonies, led the conference. Sekibo had uncovered evidence of a terrorist plot by Sapien Sunrise one week before the attack. He petitioned the UNSC for help, but they rejected his request immediately.

As the conference was coming to an end, an agreement of peace was close to being reached. Suddenly, rogue Spartan-II John-117 entered the embassy and instantly killed Richard Sekibo's bodyguard, who in reality were Sapien Sunrise infiltrators. A firefight began, in which John abducted Sekibo and created an escape path through the infiltrators by killing them. John fled the embassy alongside the Sangheili delegation, which he escorted to safety.

Outside the embassy, an evacuation ship for John was waiting. He boarded the ship, alongside the alien diplomats, and fled the planet. At some point, Sekibo was killed and his corpse was left behind in a field near the embassy on Biko. The next day, local officials discovered a signal beacon that led them to the body of Sekibo.[71][72]

By 2558, Ven III had become a hot spot for numerous Kig-Yar smugglers, black market arm dealers, and slavers. When FLEETCOM ignored the Office of Naval Intelligence's requests to assault the pirate base, ONI devised a false-flag operation involving a biological agent purportedly stolen by a Sangheili agent of Jul 'Mdama—in truth a mercenary hired by ONI—to force the Fleet to take action. Admiral Osman tasked Captain Lasky of Infinity with capturing the Sangheili and recovering the bioweapon before it could threaten human colonies. Lasky selected Spartans Gabriel Thorne and Naiya Ray for the mission and they were deployed on Ven III.[73] After Thorne was captured and Ray discovered the pirate hideout Lasky decided to involve Infinity in the mission and engaged the pirates in space and in their stronghold. Spartan Ray rescued Thorne and chased down the Sangheili agent but ONI personnel forced Ray to stand down and took the Sangheili into custody.[74]

In July 16, 2558, 'Mdama's forces and his Promethean allies attacked the human colony of Oban. The attack was repelled by a joint Spartan-UNSC Marine operation, resulting in substantial casualties on 'Mdama's side. However, the true goal of the attack had been to enable Dr. Catherine Halsey—still collaborating with 'Mdama—to establish a connection between to Infinity's slipspace engine, preventing them from jumping into slipspace. This was part of a plan to force the crew of Infinity to hand over their half of the Janus Key and allowing Halsey to unlock the Absolute Record.[63]

As part of their plan to reunite the halves of the Janus Key, Halsey and 'Mdama created a decoy Forerunner artifact that was seemingly compatible with the Key. The artifact was placed in a Forerunner structure on the uncharted planet Aktis IV along with a fake signal to draw Infinity to investigate. 'Mdama placed his troops on standby, ready to ambush the UNSC forces once they brought their half of the Janus Key to the planet. The crew of Infinity acted just as Halsey and 'Mdama had predicted, sending their half to the surface for analysis; however, Sali 'Nyon, a rebel among 'Mdama's ranks, shot the Pelican carrying the artifact down before 'Mdama had given the signal to attack and took the Key for himself. With the ambush botched, 'Mdama's concealed forces revealed themselves and attacked both Infinity and the Spartans at the Forerunner site, while Jul departed to the planet to personally eliminate the rebels and reacquire the Janus Key.[75]

The conflict continued for over seven hours, with Infinity engaged by 'Mdama's fleet while Sali 'Nyon's rebellion raged on in the Covenant's ranks. One member of 'Nyon's faction grew disillusioned with the rebellion, stole 'Nyon's Janus Key half, and offered it to 'Mdama's forces. Dr. Halsey, escorted by 'Mdama's Sangheili, traveled to the planet to reclaim the Key. Meanwhile, the Spartans in the Forerunner structure managed to use the local teleportation grid to travel to the surface, splitting into two groups with different destinations. Commander Palmer's team spotted the Sangheili defector with the Janus Key and upon overhearing his intentions, she decided to ambush Halsey once she arrived.[76] Palmer successfully captured Halsey but the doctor managed to cloud the Spartan's judgment and escape with the Janus Key. 'Mdama successfully eradicated all of Sali 'Nyon's followers on Aktis IV, ending the rebellion. Jul had Halsey retrieved and the two recombined the halves of the Janus Key, revealing the location of the Absolute Record. After the Spartans returned to Infinity, Commander Palmer told Captain Lasky that the UNSC had to prepare for the worst with the Janus Key in 'Mdama's possession.[77]

Halsey, Jul and the other humans surrounded by Sentinels inside the Absolute Record.

In September, 2558, Ayit 'Sevi, a Sangheili working with the Office of Naval Intelligence,who was able to infiltrate inside Jul's faction, provided ONI with information about Jul's progress on locating the Absolut Record. The UNSC then sent in a specialist team of Spartans Sarah Palmer, Gabriel Thorne and Holly Tanaka, Dr. Henry Glassman and 'Sevi.[78] The team infiltrated the Breath of Annihilation, hiding aboard a Type-44 Phantom piloted by 'Sevi. When 'Mdama's fleet came close to their destination — a slipspace portal to the Absolute Record, slipspace ruptures materialized into several ships of the fleet, tearing them apart, damaging Breath of Annihilation as well. The team then fought their way through the Covenant soldiers and captured another Phantom, which they used to travel to the Song of Retribution, that would successfully enter the portal.[79] Spartan Thorne and Ayit 'Sevi, who was ordered to stay behind and re-establish contact with ONI, returned to Breath of Annihilation, where the two discovered that prisoners from Retribution were being temporarily transferred to Annihilation, one of which is traitor Sali 'Nyon. 'Sevi considered using 'Nyon to create a distraction for them.

When Retribution arrived at the Absolute Record, a ForerunnerContender-class artificial intelligence detected the presence of Reclaimers aboard the ship. 'Mdama, Halsey, and numerous Sangheili Zealots traveled down to a platform below and met with the AI in order to unlock the Absolute Record. However, sensing the presence of other humans nearby, the ancila used Sentinels to transport the drop pod Spartans and Glassman were hiding in to the platform and dropped them down beside Halsey and 'Mdama. As Halsey and Glassman began to argue, an impatient Zealot attacked a Sentinel, leading to all the constructs attacking the humans and Sangheili. The AI then proceeded to translocate both groups away, while Jul's soldiers plummeted to their deaths.[80]

As the Contender began asking each party, Halsey seemingly hacked into the AI's system and disabled the ancilla, proceeding to the central chamber of the Absolute Record. With the Record's controls, Halsey ordered the Sentinels to attack Jul and his warriors. Outside the central chamber, Spartans fought off Kig-Yar and protected Dr. Glassman, but soon became cornered. However, an Aggressor Sentinel saved them and revealed it to be the Custodian in the mind of a local Sentinel, asking their help to restore it to its body.[81] The humans escorted the Sentinel to the auxiliary control conduit where they could put the Custodian back in charge of the facility. However, Halsey interfered with the attempt, halting their progress. When Palmer reached Halsey and held her at gunpoint, she was trapped inside a containment field and Halsey escaped trough the portal. Jul and his forces have managed to repel the Sentinels, and he ordered his flagship to fire into the Record, disrupting power across the station, freeing Palmer. Coming out of the portal, Halsey landed on top of the shell of the now reactivated Custodian, who had regained control and caught her, denying her further access to the Record and making the Janus Key vanish from her grasp.[82]

Sali 'Nyon's followers turning against Jul 'Mdama's forces.

Palmer regrouped with the others, but they saw the Record was suddenly disappearing into slipspace portals. Jul's forces fled the Record aboard the Song of Retribution, recovering Halsey in the process.[82]

Meanwhile, aboard Breath of Annihilation, Thorne decided to follow 'Sevi's plan and he began attacking the Sangheili in order to create panic throughout the ship. As a result, a mutiny was carried out by those who believed that the Didact's Hand lied to them about the presence of Spartans aboard the ship. Soon Thorne's location had been discovered and he was forced to escape Breath of Annihilation through a breach in the carrier's hull and dove into a swamp on the moon where the ship was undergoing repairs. During fight he was wounded by one of the Kig-Yar, but eventually Thorne managed to kill all pursuers, nearly sinking to the swamp himself in the process. At the same time, Ayit traveled to the carrier's holding cells, where he killed the guards and released ex-rebellion leader Sali 'Nyon to create more chaos on the ship. Though Sali was doubtful of his ability to lead Covenant rebels after he failed to do so the first time, Ayit manipulated him into doing so by using his zeal to inspire him.[80] 'Nyon took Ayit 'Sevi's advice to raid Jul's vault in the ship full of Forerunner artifacts from Requiem. His followers caused panic aboard the ship and 'Nyon used it to overthrow Jul's forces on the Breath. Eventually 'Nyon's forces had taken control of the ship and secured Jul's vault of Forerunner artifacts. Sali rejoiced in their victory and praised Ayit 'Sevi for their victory, still unaware that he was an ONI spy. Ayit later regrouped with Thorne and just-teleported Palmer, Tanaka, and Glassman, who he helped hide.[82]

By middle 2558, the tension between humans and Sangheili on the planet Carrow, reached a critical point. To de-escalate the situation the UNSC sent a UEG envoy, Melody Azikiwe. However, one of the influential Sangheili, Thars 'Sarov, was against this alliance. He cut a secret deal with Jiralhanae chieftain Hekabe to aid him in his upcoming uprising. On September 1, with no warning, Thars and his followers attacked other Sangheili who were looking to make peace with the humans, including his own cousin, fleetmaster Rojka 'Kasaan. The attack provided an opportunity for the Brutes to begin their invasion of the planet. They managed to destroy all communications hubs and every slipspace capable transport, forcing the citizens of Suraka to hide in underground bunkers. Unknown to Thars, Hekabe had his own motive for coming to Carrow - he wanted to uncover a Forerunner facility, buried beneath the surface, housing hundreds of Sharquoi, which he planned to use against every Sangheili who stood in his way of restoring the Jiralhanae's might.

Meanwhile, Melody Azikiwe had to complete her own secret assignment - locate and free the Spartan-II Gray Team, who according to ONI data, had been held captive on Rojka 'Kasaan's flagship Unwavering Discipline, since the end of war. As Thars attacked Rojka's people, Melody managed to get to the Spartans' cryo-chambers and wake them. Gray Team made it through numerous Sangheili, who were fighting each other, and escaped the Discipline with an injured Melody before the cruiser crash-landed on the surface of Carrow. On the ground, Melody revealed to the Spartans her ONI ties, and persuaded them to go to a local secret ONI base, Gila Station. On their way there, the team was chased by Rojka's surviving people, who in turn were being chased by Thars. When Gray Team and Melody reached the facility, they discovered that Brutes had already unearthed the Forerunner installation and were about to reach their goal. Melody convinced the Spartans to help the Surrakans and kill Hekabe before he unleashed the Sharquoi. Gray Team commandeered a Warthog and headed to Suraka before the station was attacked by Thars's people. The base was destroyed, but Melody was rescued by Rojka, who heard her speaking about Sharquoi, and decided to aid the humans in order to protect his home in Rak.

Arriving in Suraka, Gray Team regrouped with local militia and developed a plan to terminate Hekabe. The Spartans, under cover of the Surakans and the last of Rojka's people, located Hekabe. Adriana-111 shot him in the eye with a sniper rifle, but, due to his augmentations, provided by the vertex, Hekade survived the hit and returned to the Forerunner facility under the protection of Sharquoi. Melody suggested they should gain help from Thars in order to prevent Sharquoi from leaving this world. However their meeting ended with deaths of Elites including Thars himself. In final attempt to stop Hekabe Gray Team along with Melody and Rojka teamed up with Governor Ellis Gass, who planned to infiltrate the Forerunner facility, cut through the Sharquoi, and use a makeshift EMP cannon created out of an M68 Gauss cannon and the power core of a HAVOK tactical nuclear weapon mounted on a M121 Jackrabbit against Hekabe. As they reached the Chieftain and fired the EMP cannon, an electromagnetic pulse severed his connection with the Sharquoi, leaving him vulnerable. The Governor then got to Hekabe and tore the vertex from his head, adjusting it to her own. She used it to make the Sharquoi attack Hekabe and throw him into a pit of lava while making the Sharquoi aboard Hekabe's captured ships crash them, ending their threat. Ellis summoned all remaining Sharquoi to the heart of facility and activated the HAVOK, providing the others time to evacuate. As Gray Team, Melody and Rojka escaped, Ellis detonated the HAVOK, destroying the facility and all its secrets.

After a few days, Gray Team and Melody returned to the UNSC frigateUNSC Welcome to the Snipehunt, where the Spartans were offered a choice of reintegration with the UNSC as part of a specialized interspecies strike team under the Office of Naval Intelligence to continue operating deep in the Joint Occupation Zone. The Spartans reluctantly agreed to work for ONI, asking for a prowler of their own and a list of Covenant weaponry. They were also granted a formal pardon from Thel 'Vadam for destroyingGlyke as part of the deal. After scanning Carrow, the Welcome to the Snipehunt was able to determine that all of the Sharquoi appeared to have been killed in the nuclear explosion, but the UNSC planned to keep an eye on the desert in case any Sharquoi escaped before the blast.

In early October, 2558, a long-dead communications hub on Kamchatka's surface activated, attracting the attention of Jul 'Mdama and Dr. Halsey. The Covenant established an outpost while Dr. Halsey studied the relay and discovered that her old AICortana was alive and related to recent attacks on the human colonies.[84] She contacted the UNSC about her discovery, and three weeks later they sent the UNSC Infinity to retrieve her. Fireteam Osiris, a Spartan-IV special operations squad, was deployed on the surface. Spartans fought their way through Jul's soldiers, who suddenly came under attack by Prometheans at the same time. The chaos from the Prometheans' rebellion provided Osiris cover from the Covenant, allowing them to sneak to the temple where 'Mdama and Halsey were stationed. After reaching the temple, Osiris killed Zealot guards and then turned to Jul himself, who was killed attempting to fight off Spartan Jameson Locke. Spartans then took Dr. Halsey under custody and brought her back to the Infinity.[85] With Jul 'Mdama dead and the Prometheans now against them, his Covenant troops became desperate. Some of them fled the system, but most of the rest regrouped on Sanghelios, attempting an attack on the Vadam clan burial grounds in hopes of a revenge attack against the Arbiter.

On October 24, 2558, Blue Team was deployed from the UNSC Infinity on Pelican with mission to locate and secure Argent Moon, a derelict ONI research and development station.[86] Boarding the station, Spartans discovered that it was occupied by Covenant scavengers. Blue Team's initial plan was to fight their way to Central Control, where they could shut off Argent Moon's gravity and life support systems, and so flush out its decks of any remaining hostiles. However, on their way to Central Control's location, they were ambushed by a Hunter pair, who broke the catwalk they were on and sent them down to the maintenance tunnels several stories below. At the bottom, Blue Leader John-117 experienced a vision of a seemingly-alive Cortana, urging him to follow her to Meridian.[86] As Blue Team continued with their mission, they witnessed the arrival of remnants of the Jul 'Mdama's fleet. Finding themselves outnumbered, the Spartans decided to scuttle Argent Moon, denying it to the Covenant. They proceeded to overload the station's reactor by shutting off its safeties. The resulting explosion would destroy the station, the Covenant aboard, and any Covenant warships surrounding it. In order to escape the blast, Blue Team commandeered a Winter-class prowlerONI Acrisius parked in a hangar. Before the evacuation, John radioed the UNSC Infinity and informed them that he would be reassigning Blue Team to Meridian. However, Infinity ordered John back to them while another Spartan team was sent to deal with Cortana. Nevertheless, John and the rest of Blue Team decided to head to Meridian and find Cortana, disobeying direct orders. The Spartans then evacuated aboard Acrisius, leaving Argent Moon as it exploded and killed all the Covenant in its vicinity.[86]

After the disappearance of Blue Team, the UNSC declared them AWOL and tasked Fireteam Osiris with locating and bringing them into the custody.

Osiris arrived at Meridian to find it under attack by Prometheans, with the colonists in desperate need of assistance to fend off the invaders. In exchange for Governor Sloan's cooperation, Osiris agreed to help repel the Prometheans' attack while looking for clues about Blue Team's whereabouts.[87][88] Accessing Blue Team's abandoned prowler's data banks led Osiris to the mines underneath Apogee Station, where they discovered a massive Forerunner structure guarded by the Warden Eternal, an ancilla that served as the protector of the Domain and claimed his loyalty belonged to Cortana. After eliminating the Warden, Osiris came across a dormant Guardian as well as Blue Team, who were boarding the Guardian itself.[89] After ordering the Spartan-IIs to stand down, to no avail, Spartan Locke attempted to detain the Master Chief. In the resulting hand-to-hand fight, John-117 eventually gained the upper hand and used Locke's own armor restraint against him. After Blue Team entered the Guardian, the construct began to rise from its underground sanctuary. Osiris managed to return to Meridian's surface, where they discovered that the colony was being evacuated. The Spartans fought their way through to their Pelican, boarding it moments before the Guardian entered slipspace, devastating the colony.[90]

Around the same time, CommanderMaya Sankar, an undercover operative of the Office of Naval Intelligence, known among the Insurrectionists as FERO, was tasked with gathering intel on the situation on one of the recently destroyed colonies by infiltrating the New Colonial Alliance, which held a large presence on the colony, with help from the AI Black-Box.[91] Arriving at Conrad's Point, Maya infiltrated the rebel base, where she discovered the insurrectionist leader Ilsa Zane. Upon the discovery of Zane, ONI assessed that the opportunity to strike was at its greatest and immediately called in an airstrike on the location. As Maya attempted to leave, Ilsa confronted her and nearly killed her, only being stopped by the beginning of the airstrike. Maya managed to escape and proceeded to an unsanctioned safehouse where she was secretly keeping Mshak Moradi, to seek his help involving the anomalies that apparently destroyed Conrad's Point and allegedly killed the Master Chief John-117. Once Black-Box and Mshak were able to determine the next appearance of the anomalies, Maya headed to Laika III to attempt to warn the colonists of the impending danger. However, she was attacked by a vengeful Ilsa Zane, who had tracked Maya down. As the Guardian began to rise from its shelter, Maya attempted to broadcast about the destruction to the rest of the outer colonies, warning them that the UNSC would not help them. She was then killed by Bostwick, one of FERO's followers, to preserve her as an icon and a martyr for the outer colonies.[92]

Fireteam Osiris fighting alongside the Swords of Sanghelios against the remnants of Jul 'Mdama's Covenant.

In late October, 2558, the clash between remnants of Jul 'Mdama's Covenant and Arbiter's Swords of Sanghelios on Sanghelios reached its peak. On October 27, the Covenant managed to corner Thel 'Vadam to the Elder Council Chamber in Nuusra. However, the warriors of 'Vadam, with the help from Spartan-IV Fireteam Osiris, broke through enemy lines and evacuated the Arbiter to his base camp.[93] There, Spartan Locke revealed that they arrived on Sanghelios to ask for 'Vadam's help in reaching a yet dormant Guardian at Sunaion, in order to follow Blue Team. According to the plan, developed by Dr. Halsey, the Spartans, with the aid of the Swords of Sanghelios, would obtain a Forerunner Constructor from one of the Guardian's nearby support stations, which would allow Halsey to activate the Guardian.[94][95] As the Constructor took off, the joint force of Spartans and Swords of Sanghelios followed it with a squadron of air vehicles to Sunaion - the last bastion of Jul 'Mdama's Covenant on Sanghelios. While the Arbiter led his forces against the Covenant directly, Osiris destroyed Covenant anti-air emplacements to allow the Arbiter's fleet to move in closer to the city. When the Guardian began rising out of the sea nearby, the buildings around were ripped apart. The Spartans then regrouped with the Arbiter, who was engaging Promethean forces, led by the Warden Eternal, now utilizing another physical body. After a lengthy engagement, the five destroyed the Warden and the nearby Prometheans just as the Guardian prepared to leave. While the Arbiter remained behind to finish eliminating Covenant and Promethean forces, Spartan Sarah Palmer and Dr. Halsey picked up Osiris in the Pelican and flew towards the Guardian. A pursuing Banshee damaged the dropship, though Palmer was still able to drop Osiris off on the Guardian's surface just as it entered slipspace and left Sanghelios. The Guardian severely damaged Sunaion with both its concussive blasts and its departure into slipspace, and parts of the city began collapsing into the water below. However, 'Vadam was successful in leading the Swords of Sanghelios in eliminating the remaining Covenant forces in the damaged city, ending the battle.[96]

After arriving on Genesis, a Forerunner Builder installation, Blue Team fought their way through Covenant forces who had crashed landed there. They eventually reached a structure where they encountered the Warden Eternal, who introduced himself as Cortana's defender and simultaneously deployed several waves of Prometheans to confront the Spartans. After an extended battle, Blue Team were able to defeat the Prometheans, destroying one of the Warden's bodies in the process. Immediately afterward, Blue Team were contacted by Cortana, who informed them of her intention to uphold the Mantle of Responsibility. Fighting their way through several more Promethean squadrons, Blue Team eventually reached the structure known as the Gateway, described as a link between Genesis and the Domain.[97]

Fireteam Osiris arrived on Genesis roughly 48 hours later. Upon arriving on the installation, Osiris encountered its monitor, 031 Exuberant Witness, who offered to assist the Spartans in retrieving Blue Team and preventing Cortana from claiming the Mantle. After fighting through the battling forces of the Covenant and Prometheans, Osiris finally reached Blue Team's location and offered to help the Master Chief stop Cortana. In an attempt to prevent John and Blue Team from returning to the UNSC, Cortana transported them to an unidentified location within the interior of the Gateway. Blue Team made their way to Cortana's position after battling through numerous waves of Prometheans and several of the Warden Eternal's bodies. John attempted to persuade Cortana to end her rebellion and return, but Cortana refused and placed Blue Team inside a Cryptum.[98] Learning what happened, Osiris and Exuberant Witness managed to narrowly wrest the Cryptum from Cortana's control before she could transport it aboard a Guardian and flee into slipspace. Exuberant's Constructors opened the Cryptum and Blue Team was reunited with Osiris, who promptly exfiltrated them to Sanghelios, where they regrouped with Thel 'Vadam and his Swords of Sanghelios.[99]

On October 28, 2558, Cortana began to deploy her Guardians from Genesis throughout the galaxy. In tandem, various human AIs that had pledged their loyalty to her cause started to shut down electronic devices and networks on multiple colony worlds. From Genesis, Cortana broadcast an offer of acceptance of her new order and a threat of violence, consummation, and remaking to those who resist. Guardians orbiting Earth and other worlds unleashed massive electromagnetic pulses which knocked out the power of every orbital defense platform and warship, leaving them to drift aimlessly or fall and crash on the surface of planets below. A notable exception was the UNSC Infinity, which managed to escape.[100] The Created were quick to spread their influence across the galaxy's inhabited worlds, while utilizing Forerunner machinery and UNSC information systems to turn terraforming equipment and world engines to their own designs.[101] After removing its human crew, the Created used Lethbridge Industrial's Auriga Station to build new weapons and tools by constructs loyal to Cortana.[102] However due to failsafe measures on Installation 00 the Created were unable to access the Ark.[103] UNSC logistics AI Isabel and science personnel were stranded on Installation 00 as a result of the portal closing without warning, forcing them to fight for survival without support from UNSC.[104]

A month later, after Cortana unleashed Guardians on the galaxy, on November 25, a violent mercenary faction known as the Banished, led by the Jiralhanae warlord Atriox, arrived at the Ark and sought to take control of it.[105] They slaughtered all of the humans at the Henry Lamb Research Outpost, leaving no survivors but the logistics AI, Isabel. Four months later, on March 28, 2559, after 28 years of drifting, the UNSC Spirit of Fire arrived at the Ark. Awakened from cryo-sleep, the crew under command of Cpt. James Cutter attempted to re-establish contact with UNSC. In order to do that, Spartan-II Red Team was deployed and tasked with investigating the distress signal coming from the surface. There they encountered Isabel and Atriox, who managed to severely wound Douglas-042 and forced the Spartans to retreat back to Spirit of Fire.[106]

In the next few days the Spirit of Fire ground teams led by the members of Red Team conducted multiple offensives against the Banished, including disrupting their salvage operations,[107] crippling their portal network[108] and destroying Atriox's flagship, the CAS-class assault carrierEnduring Conviction.[109] During this time it was discovered that the Ark's Foundry had created a new replacement for Installation 04. A race for the Halo began: Atriox wanted to use it against the humans and Cpt. Cutter planned to disarm it and send it to the location of the original ring with a distress beacon, which would draw UNSC reinforcements to the Ark.[110] Eventually the Spirit of Fire crew got the upper hand and in the final battle over Halo's control room they eliminated all Banished forces on the ring.[111] The UNSC forces managed to evacuate from Halo just before it entered slipspace for the Soell system; however, Prof. Ellen Anders became stranded inside the control room and left the Ark with the Halo, which was intercepted in slipspace by one of the Created's Guardians. On the Ark, both Cpt. Cutter and Atriox began planning their next moves against each other, not willing to leave the Ark to one another.[112]

The battle continued for months draining strength of both sides. Eventually two months after the departure of Installation 09, Atriox gathered a salvage operation and sent them to scout the area near the wreckage of High Charity with warning not to go inside. Arriving at the area Banished forces under command of Brute brothers Voridus and Pavium disabled the Sentinel defense network around High Charity. In order to salvage something valuable Voridus breached the energy barrier and entered the destroyed Covenant holy city, despite Atriox's warning. However that breach provided an exit to the Flood, which had built itself up from spores that had survived the detonation of High Charity's backup reactor and the firing of Installation 08 in 2552 at the end of the Human-Covenant War.[113] Flood forces managed to push back the Banished and take a hold over territory around High Charity, creating a Proto-Gravemind. Ultimately the survivng Banished forces reactivated the Forerunner defenses and with their help destroyed the Proto-Gravemind before it became a Gravemind. Not pleased with their loses, Atriox ordered his lieutenants to secure the breach in the barrier, while the Ark's Sentinels would neutralize all escaped Flood forces.[114]

↑Halo: Fractures-Halo: Shadow of Intent-Page 140-"They killed his du'nak too?" The boy's voice cracked between a snarl and a sob. He gave the nearest Jiralhanae
a ferocious kick. "I hate them all!" The Jiralhanae's body barely moved.

↑Canon Fodder"The resulting conflict would be called the Great Schism, and it would divide the Covenant into two, ultimately forcing the Sangheili out."

↑ 15.015.1Halo: Evolutions : The Return, "It was a terrible war. The Prophets provided the Brutes with powerful new weapons, hoping that they would in turn defend their Prophets against our wrath. But when the Prophets went into hiding, the lack of leadership allowed the Brutes to return to their savage nature and they soon began to fight against each other. This lack of solidarity made them much easier prey. Some of my fellow commanders continue that fight even now."